A plurality of rollers are contained in generally conventional printing presses, such as web-fed rotary printing presses, for example. Inking rollers, in particular, are provided in such presses, which inking rollers are used for transferring ink from an ink reservoir to the plate cylinder. It is possible to meter the ink that is transferred to the plate cylinder by the inking rollers, so that the ink is being transferred as a uniform film of a defined thickness. Because of this, it is possible to compensate for interferences, such as for example, fluctuations in speed and rotary vibrations.
Dampening rollers can also be provided. These dampening rollers transfer a dampening agent, for example water, to the printing group.
Pairs of rollers are often formed by rollers which are in engagement with each other. At least one of the rollers in the pair has a cylinder surface made of an elastic material, so that this cylinder surface can be deformed at least slightly, depending on the contact pressure exerted on it by the roller opposite it. As a result, a contact area, which extends in a straight line between the rollers, and which is called a contact strip, appears because of the elastic deformation of the roller surface. The circumferential width of the contact strip can be varied by adjusting the contact pressure between the rollers. The width of this contact strip has a considerable effect on the print result. If, for example, the contact strip in an inking unit is too narrow, not enough ink is being transferred. In cases in which the contact strips are too wide, the elastic roller can be damaged by the kneading effect occurring because of this excessively wide contact strip.
To be able to always correctly adjust the strip width, in particular as a function of the press operating conditions, for example the temperature of the printing presses or their degree of wear, it is necessary to seat one of the rollers displaceably. This displaceably seated roller can be pushed, by an actuator, with an adjustable force, in a direction toward the opposite roller. Once the correct contact pressure between the two rollers has been found, a fixation device for use in fixing the first roller in place, with respect to the second roller, is operated to maintain the contact pressure permanently.
A device for setting a contact pressure between two rollers is known from DE 197 19 305 A1. By use of the seating arrangement described in that document, the displaceably seated roller is pressed against the opposite roller by a spring, which spring is supported on the frame of the printing press. Because of this spring-biased roller displacement, a defined contact pressure between the two rollers always occurs as a function of the respectively selected characteristic curve of the spring. A clamping mechanism, with a clamping lever and with a clamping plate, and useable for fixing the roller in the pressed-on place, is described, by the use of which clamping mechanism the roller shaft can be fixed in place on the frame of the printing press by a frictional connection.
A device for the semi-automatic adjustment of rollers is known from DE 199 19 733 A1. An adjustably seated roller is maintained in a roller holder, which, in turn, is seated in a frame holder that is fixedly arranged on the frame. In this case, the roller holder and the frame holder can be displaced, in relation to each other, and are connected with each other by a spring-elastic assembly. The spring-elastic assembly here has a defined prestress, so that the roller, which is displaceably seated on the roller holder, can be pressed against the opposite roller with a defined contact pressure. Arresting bolts are provided for use in fixing the roller holder in place on the frame holder, and by whose advancement, the roller holder can be clamped, in a frictionally connected manner, on the frame holder.
DE 38 08 142 A1 describes a device for seating two cylinders. In this case, a contact pressure between two rollers, which two rollers can be placed against and away from each other, can be changed by altering the pressure of a pressure medium. A switching device is also provided, by use of which, the pressure medium can be selectively conducted to different actuators.
DE-OS 16 11 303 discloses a device for bringing a printing cylinder of a rotogravure press into and out of contact. A pressure reduction valve is provided.
Inking rollers are known from U.S. Pat. No. 2,774,301 and GB 1 213 935. These rollers can be brought into contact by the use of actuators which are operated by a pressure medium. Here, a valve for setting the level of the pressure and at least one shut-off valve are provided.